JP5822669B2 - Copper foil for producing graphene and method for producing graphene using the same - Google Patents

Description

  The present invention relates to a copper foil base material for producing graphene, and a method for producing graphene using the same.

  Graphite has a layered structure in which a number of flat carbon 6-membered ring layers are stacked, and those having a single atomic layer to several atomic layers are called graphene or graphene sheets. Graphene sheets have unique electrical, optical and mechanical properties, and in particular have a high carrier moving speed. Therefore, graphene sheets are expected to have a wide range of applications in the industry, such as fuel cell separators, transparent electrodes, conductive thin films for display elements, mercury-free fluorescent lamps, composite materials, and drug delivery system (DDS) carriers. ing.

As a method of producing a graphene sheet, a method of peeling graphite with an adhesive tape is known, but the number of layers of the obtained graphene sheet is not constant, it is difficult to obtain a large area graphene sheet, and it is not suitable for mass production There's a problem.
Thus, a technique (chemical vapor deposition (CVD) method) has been developed in which a graphene sheet is grown by bringing a carbon-based material into contact with a sheet-like single crystal graphitized metal catalyst and then performing heat treatment (Patent Literature). 1). As this single crystal graphitized metal catalyst, a metal substrate of Ni, Cu, W or the like is described.
Similarly, a technique for forming graphene by chemical vapor deposition on a copper layer formed on a Ni or Cu metal foil or Si substrate has been reported. The graphene film is formed at about 1000 ° C. (Non-patent Document 1).

JP 2009-143799 A

SCIENCE Vol.324 (2009) P1312-1314

However, as in Patent Document 1, it is not easy to manufacture a single crystal metal substrate, which is extremely expensive, and it is difficult to obtain a large-area substrate, and thus it is difficult to obtain a large-area graphene sheet. . On the other hand, Non-Patent Document 1 describes that Cu is used as a substrate, but graphene does not grow in the surface direction in a short time on the Cu foil, and the Cu layer formed on the Si substrate is annealed. The substrate is formed as coarse particles. In this case, the size of graphene is limited by the Si substrate size, and the manufacturing cost is high.
That is, an object of the present invention is to provide a copper foil for producing graphene capable of producing large-area graphene at low cost and a method for producing graphene using the same.

  The copper foil for producing graphene of the present invention has a 60 ° gloss in the parallel and perpendicular directions of rolling of 500% or more, contains 20% by volume or more of hydrogen, and is heated at 1000 ° C. for 1 hour in the atmosphere of the remaining argon. The later average crystal grain size is 200 μm or more.

  The average crystal grain size is preferably 400 μm or more, more preferably 900 μm or more, and the arithmetic average roughness Ra of the surface is preferably 0.05 μm or less.

Further, the copper foil for producing graphene of the present invention contains 20% by volume or more of hydrogen, and the average crystal grain size after heating for 1 hour at 1000 ° C. in the atmosphere of the remaining argon is 200 μm or more, and the arithmetic average roughness of the surface Ra is 0.05 μm or less. The arithmetic average roughness Ra of the surface is preferably 0.03 μm or less.

  In the copper foil for graphene production of the present invention, Sn is tough pitch copper specified in JIS-H3100 or JIS-H3250, oxygen-free copper specified in JIS-H3100 or JIS-H3510, or the tough pitch copper or the oxygen-free copper. And it is preferable to contain 0.050 mass% or less of 1 or more types of elements chosen from the group of Ag.

  The method for producing graphene of the present invention uses the copper foil for producing graphene, arranges the heated copper foil for producing graphene in a predetermined chamber and supplies a carbon-containing gas, and the surface of the copper foil for producing graphene A graphene forming step of forming graphene on the surface, and a graphene transfer step of laminating a transfer sheet on the surface of the graphene and transferring the graphene onto the transfer sheet while removing the graphene-producing copper foil by etching .

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil which can produce a large area graphene at low cost is obtained.

It is process drawing which shows the manufacturing method of the graphene which concerns on embodiment of this invention.

  Hereinafter, the copper foil for graphene manufacture which concerns on embodiment of this invention is demonstrated. In the present invention, “%” means “% by mass” unless otherwise specified.

<Composition>
As the copper foil for producing graphene, tough pitch copper (TPC) standardized to JIS-H3250 or JIS-H3100, or oxygen-free copper (OFC) standardized to JIS-H3510 or JIS-H3100 can be used.
Moreover, the composition which contains 0.050 mass% or less of 1 or more types of elements chosen from the group of Sn and Ag with respect to these tough pitch copper or oxygen-free copper can also be used. When the above elements are contained, the strength of the copper foil is improved, the film has an appropriate elongation, and the crystal grain size can be increased. If the content of the element exceeds 0.050% by mass, the strength is further improved, but the elongation is lowered and the workability is deteriorated and the growth of the crystal grain size may be suppressed. More preferably, the content of the element is 0.040% by mass or less.
In addition, the lower limit of the content ratio of the element is not particularly limited, but 0.005% by mass can be set as the lower limit, for example. When the content ratio of the element is less than 0.005% by mass, it may be difficult to control the content ratio because the content ratio is small.

<Thickness>
The thickness of the graphene-producing copper foil is not particularly limited, but is generally 5 to 150 μm. Furthermore, it is preferable to set the thickness of the copper foil to 12 to 50 μm in order to easily perform the etching removal described later while ensuring the handleability. When the thickness of the copper foil for producing graphene is less than 12 μm, it is easy to break and the handling property is inferior, and when the thickness exceeds 50 μm, it may be difficult to remove by etching.

<60 degree gloss>
Both the 60-degree glossiness (JIS Z 8741) in the rolling parallel direction and the perpendicular direction of rolling of the copper foil for producing graphene is 500% or more.
As will be described later, after producing graphene using the copper foil for producing graphene of the present invention, it is necessary to transfer the graphene from the copper foil to the transfer sheet. However, if the surface of the copper foil is rough, transfer is difficult. Was found to be damaged. Therefore, 60 degree glossiness is defined as an index representing the surface roughness of the copper foil.
If any of the 60 ° gloss in the direction parallel to rolling and the direction perpendicular to rolling is less than 500%, the graphene is damaged during transfer. The upper limit of the 60-degree glossiness in the rolling parallel direction and the direction perpendicular to the rolling direction is not particularly limited, but about 800% is practically the upper limit.
In order to facilitate the transfer of graphene to the transfer sheet as described above, the arithmetic average roughness Ra of the copper foil surface for producing graphene specified in JIS B0601 is preferably 0.05 μm or less, and Ra is 0.03 μm or less. It is more preferable that The lower limit of Ra need not be particularly limited, but the lower limit of Ra on the copper foil surface that can be produced is considered to be about 0.01 μm.

<Average crystal grain size>
The copper foil for producing graphene contains 20% by volume or more of hydrogen, and the average crystal grain size after heating for 1 hour at 1000 ° C. in the atmosphere of the remaining argon is 200 μm or more.
If the average crystal grain size of the copper foil for producing graphene is smaller than 200 μm, it becomes an obstacle when growing graphene on the surface of the copper foil for producing graphene, and it becomes difficult for graphene to grow in the plane direction. This is presumably because the crystal grain boundaries hinder the growth of graphene. In particular, the average crystal grain size of the copper foil for producing graphene is preferably 900 μm or more.
In addition, heating for 1 hour at 1000 ° C. in an atmosphere of 20% by volume or more of hydrogen and the remainder of argon is a condition for heating the copper foil for producing graphene to the decomposition temperature of the carbon-containing gas or higher when producing graphene. It is imitated.
In addition, the average crystal grain size is measured for a graphene-producing copper foil by the cutting method of JIS H0501.

  By using the graphene-producing copper foil defined as described above, large-area graphene can be produced at a low cost and with a high yield.

<Manufacture of copper foil for graphene production>
The copper foil for producing graphene according to the embodiment of the present invention can be produced, for example, as follows. First, after manufacturing the copper ingot of a predetermined composition and performing hot rolling, annealing and cold rolling are repeated and a rolled sheet is obtained. The rolled sheet is annealed and recrystallized, and finally cold-rolled to a predetermined thickness of 80 to 99.9% (preferably 85 to 99.9%, more preferably 90 to 99.9%). To obtain copper foil.

Here, it is important to control the 60 degree gloss of the copper foil for producing graphene to 500% or more. As the method, both oil film equivalents of the final pass of the final cold rolling and the pass before the final pass of the final cold rolling are set to 18000 or less.
The rolled copper foil is generally processed at high speed under oil lubrication, but the shear band deformation tends to become dominant as the lubricating oil film becomes thinner. This is a phenomenon common to metals in general. Note that the presence of a shear band is not preferable for the growth of crystal grains when annealed. And the some or short depth of a shear band can be represented by the glossiness of the copper foil surface. Specifically, as a phenomenon during rolling, if the oil film introduced between the roll and the material is thick, oil pits (unevenness) are formed on the rolled surface, but if the oil film is thin, it contacts the rolling roll on the material surface. The area increases and free deformation is limited, oil pits do not develop, the smooth surface profile of the rolling roll is transferred, and a smooth surface is formed. Therefore, the oil film equivalent is set to 18000 or less as an index for thinning the oil film. If the oil film equivalent exceeds 18000, the 60 degree glossiness of the copper foil surface will be less than 500%.

The oil film equivalent is represented by the following formula.
(Oil film equivalent) = {(rolling oil viscosity, kinematic viscosity at 40 ° C .; cSt) × (rolling speed; m / min)} / {(yield stress of material; kg / mm ² ) × (roll biting angle; rad )}
In order to make the oil film equivalent 18000 or less, it is preferable that the rolling oil viscosity (kinematic viscosity at 40 ° C.) is low, the rolling speed is low, and the roll biting angle (corresponding to the reduction amount) is large. For example, the viscosity is 3 by a rolling roll having a roll diameter of 250 mm or less and a surface roughness Ra _roll adjusted to 0.1 μm or less (preferably 0.01 to 0.04 μm, more preferably 0.01 to 0.02 μm). -8 cSt (preferably 3-5 cSt, more preferably 3-4 cSt), rolling speed 100-500 m / min (preferably 200-450 m / min, more preferably 250-400 m / min), pass A rolling reduction of 10 to 60% can be mentioned. The roll biting angle is, for example, 0.001 to 0.04 rad, preferably 0.002 to 0.03 rad, and more preferably 0.003 to 0.03 rad.

When the surface roughness Ra _roll of the rolling roll exceeds 0.1 μm, irregularities on the roll surface are transferred, and the smoothness of the material surface is impaired. By rolling under the above conditions, the area of the flat surface portion without oil pits can be increased. If the viscosity of the rolling oil exceeds 8 cSt, the oil film equivalent becomes large and surface gloss cannot be obtained. On the other hand, if it is less than 3 cSt, the rolling resistance increases and the rolling reduction cannot be increased. When the rolling speed exceeds 500 m / min, the amount of introduced oil increases and the glossiness decreases. On the other hand, when the rolling speed is less than 100 m / min, a sufficient amount of reduction cannot be obtained, which is disadvantageous from the viewpoint of productivity.
If the rolling reduction exceeds 99.9%, work hardening proceeds and the deformability is lost, and the rolling reduction in the final pass cannot be secured. On the other hand, if the rolling reduction is less than 80%, the rolling texture does not develop and surface smoothness is obtained. I can't. If the roll bite angle exceeds 0.04 rad, the difference between the roll peripheral speed and the material speed increases, and the smoothness of the material surface is impaired. On the other hand, if it is less than 0.002 rad, the amount of oil that enters between the rolling roll and the material to be rolled and plays the role of lubrication is large, and the gloss is lowered.
The rolling reduction for each pass is, for example, 20 to 40%, preferably 20 to 35%, and more preferably 25 to 35%. When the rolling reduction exceeds 35%, a shear band develops, an oil pit is generated, and the glossiness is lowered. On the other hand, if it is less than 20%, the number of passes increases, so the productivity deteriorates.

  Another method for controlling the 60 degree gloss of the copper foil for producing graphene to 500% or more is to increase the material temperature during the final cold rolling. When the material temperature is raised, dislocation recovery occurs and shear band deformation is less likely to occur. The material temperature is meaningless at the temperature at which oil lubricity is impaired or the copper foil is recrystallized, and may be 120 ° C. or less, preferably 100 ° C. or less. Further, when the material temperature is 50 ° C. or less, there is almost no effect of suppressing shear band deformation.

By the above method, the 60 degree glossiness of the copper foil for producing graphene can be controlled to 500% or more. It has also been found that when the 60-degree glossiness of the copper foil is 500% or more, the crystal grain size after annealing is 200 μm or more. This is presumably because crystal growth after annealing is promoted by controlling the oil film equivalent and the material temperature during the final cold rolling to make shear band deformation difficult to occur.
In addition, the method of controlling the 60 degree glossiness of the copper foil for producing graphene to 500% or more is not limited to the above.

<Graphene production method>
Next, with reference to FIG. 1, a method for producing graphene according to an embodiment of the present invention will be described.
First, the graphene producing copper foil 10 of the present invention described above is placed in a chamber (vacuum chamber or the like) 100, the graphene producing copper foil 10 is heated by the heater 104, and the inside of the chamber 100 is decompressed or evacuated. . Then, the carbon-containing gas G is supplied from the gas inlet 102 into the chamber 100 (FIG. 2A). Examples of the carbon-containing gas G include, but are not limited to, carbon dioxide, carbon monoxide, methane, ethane, propane, ethylene, acetylene, alcohol, and the like. Good. Further, the heating temperature of the graphene-producing copper foil 10 may be equal to or higher than the decomposition temperature of the carbon-containing gas G, for example, 1000 ° C. or higher. Further, the carbon-containing gas G may be heated to a decomposition temperature or higher in the chamber 100, and the decomposition gas may be brought into contact with the copper foil 10 for producing graphene.
Thereby, decomposition gas (carbon gas) forms the graphene 20 on the surface of the copper foil 10 for graphene manufacture (FIG.2 (b)).

And the copper foil 10 for graphene manufacture is cooled to normal temperature, the transfer sheet 30 is laminated | stacked on the surface of the graphene 20, and the graphene 20 is transcribe | transferred on the transfer sheet 30. FIG. Next, this laminated body is continuously immersed in the etching tank 110 through the sink roll 120, and the copper foil 10 for graphene production is removed by etching (FIG. 2C). Thus, the graphene 20 laminated on the predetermined transfer sheet 30 can be manufactured.
Furthermore, when the laminated body from which the copper foil 10 for producing graphene is removed is pulled up, the substrate 40 is laminated on the surface of the graphene 20, and the transfer sheet 30 is peeled off while transferring the graphene 20 onto the substrate 40, The stacked graphene 20 can be manufactured.

  As the transfer sheet 30, various resin sheets (polymer sheets such as polyethylene and polyurethane) can be used. As an etching solution for etching and removing the copper foil 10 for producing graphene, for example, a sulfuric acid solution, a sodium persulfate solution, hydrogen peroxide, a sodium persulfate solution, or a solution obtained by adding sulfuric acid to hydrogen peroxide can be used. As the substrate 40, for example, Si, SiC, Ni, or Ni alloy can be used.

<Preparation of sample>
After producing a copper ingot having the composition shown in Table 1 and performing hot rolling at 800 to 900 ° C., annealing and cold rolling are repeated once in a continuous annealing line at 300 to 700 ° C. to roll a thickness of 1 to 2 mm. I got a plate. This rolled sheet was annealed and recrystallized in a continuous annealing line at 600 to 800 ° C., and finally cold-rolled to a thickness of 7 to 50 μm with a reduction ratio of 95 to 99.7%. Examples 1 to 15 and Comparative Examples 1 to 9 copper foils were obtained.

Here, the oil film equivalents of both the final pass of the final cold rolling and the pass before the final pass of the final cold rolling were adjusted to the values shown in Table 1.
The oil film equivalent is represented by the following formula.
(Oil film equivalent) = {(rolling oil viscosity, kinematic viscosity at 40 ° C .; cSt) × (rolling speed; m / min)} / {(yield stress of material; kg / mm ² ) × (roll biting angle; rad )}

<Measurement of 60 degree glossiness>
For the copper foils of Examples 1 to 15 and Comparative Examples 1 to 9, 60% of the surface after final cold rolling and after heating at 1000 ° C. for 1 hour in an atmosphere of 20% by volume or more of hydrogen and the balance argon. Glossiness was measured.
The 60 degree glossiness was measured using a gloss meter (trade name “PG-1M” manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-Z8741.

<Measurement of surface roughness (Ra, Rz, Sm)>
About the copper foils of Examples 1 to 15 and Comparative Examples 1 to 9, the surface roughness after final cold rolling and after heating for 1 hour at 1000 ° C. in an atmosphere of argon containing the remaining 20% by volume of hydrogen. Was measured.
Using a contact roughness meter (trade name “SE-3400”, manufactured by Kosaka Laboratories), the arithmetic average roughness (Ra; μm) based on JIS-B0601 was measured, and the oil pit depth Rz was JIS B0601-. Ten-point average roughness was measured according to 1994. The measurement position is changed 10 times in parallel with the rolling direction under the conditions of a measurement standard length of 0.8 mm, an evaluation length of 4 mm, a cut-off value of 0.8 mm, and a feed rate of 0.1 mm / second, and 10 times in each direction. The value in the measurement was obtained. In addition, the average interval of unevenness (Sm; mm) is a measurement position parallel to the rolling direction under the conditions of a measurement reference length of 0.8 mm, an evaluation length of 4 mm, a cut-off value of 0.8 mm, and a feed rate of 0.1 mm / second. The measurement was repeated 10 times, and the values for 10 measurements were obtained. Note that Sm is defined as “average interval of unevenness” in JIS B0601-2001 (conforms to ISO 4287-1997) in which the surface property is expressed by a contour curve method, and the contour length of each unevenness within the reference length. The average of

<Measurement of average crystal grain size>
About the copper foil of Examples 1-15 and Comparative Examples 1-9, the average crystal grain diameter of the surface was measured with the cutting method of JISH0501.

<Manufacture of graphene>
The copper foil of each example (length and width 100 × 100 mm) was placed in a vacuum chamber and heated to 1000 ° C. Methane gas is supplied to this vacuum chamber under vacuum (pressure: 0.2 Torr) (supply gas flow rate: 10 to 100 cc / min), and the copper foil is heated to 1000 ° C. in 30 minutes and then held for 1 hour. Graphene was grown on the surface.
About each Example, manufacture of graphene was performed 10 times on the said conditions, and the presence or absence of the graphene on the surface of copper foil was observed and evaluated by atomic force microscope (AFM). The case where scaly irregularities were observed on the entire surface by AFM was regarded as the production of graphene, and the yield was evaluated according to the following criteria based on the number of times graphene was produced out of 10 productions. If the evaluation is ◎, ○ or △, there is no practical problem.
◎: Graphene was produced 5 times or more out of 10 productions ○: Graphene was produced 4 times out of 10 productions △: Graphene was produced 3 times out of 10 productions × : Of 10 times of production, the number of times graphene was produced is 2 times or less

The obtained results are shown in Table 1. In Table 1, G60 _RD and G60 _TD indicate 60-degree glossiness in the rolling parallel direction and the rolling perpendicular direction, respectively. GS represents an average crystal grain size.
“TPC” in Examples 1 to 7, Example 14, Example 15, Comparative Examples 1 to 3, and Comparative Examples 7 and 9 in the table represents tough pitch copper standardized to JIS-H3100. “OFC” in Examples 9 to 12, Comparative Examples 4 to 6, and Comparative Example 8 represents oxygen-free copper specified in JIS-H3100. TPC of Example 13 represents tough pitch copper standardized to JIS-H3250. OFC in Example 8 represents oxygen-free copper specified in JIS-H3510.
Therefore, “OFC + Sn 1200 ppm” in Comparative Example 8 represents that 1200 wtppm of Sn was added to oxygen-free copper specified in JIS-H3100.

As is apparent from Table 1, the 60 ° glossiness of the copper foil surface is 500% or more, the average crystal grain size after heating for 1 hour at 1000 ° C. in an atmosphere containing 20% by volume or more of hydrogen and the balance argon. In the case of Examples 1 to 15 having a thickness of 200 μm or more, the graphene production yield was excellent.
In particular, in the case of Examples 1 to 6, 8, 9, 11, 13 and 15 in which 20% by volume or more of hydrogen is contained and the average crystal grain size after heating for 1 hour at 1000 ° C. in the atmosphere of argon is 900 μm or more The graphene production yield was the best. In the case of Examples 7 and 10 in which the average crystal grain size after heating for 1 hour at 1000 ° C. in an atmosphere of argon containing 20% by volume or more of hydrogen is 400 to 900 μm, the average crystal grain size is less than 400 μm. Compared to Example 14, the graphene production yield was excellent.

  On the other hand, the oil film equivalent of both the final cold rolling final pass and the pass immediately before the final cold rolling pass exceeded 18000, and the 60-degree glossiness of the surface of the copper foil itself was less than 500%. In Comparative Examples 1 to 9, the production yield of graphene was inferior. Further, in the case of Comparative Examples 1 to 9, the average crystal grain size after heating for 1 hour at 1000 ° C. in an atmosphere of argon containing 20% by volume or more of the balance was less than 200 μm. This is considered to be because the rolling oil film equivalent was too much, and a shear band was generated to suppress the growth of crystal grains.

10 Copper foil for graphene production 20 Graphene 30 Transfer sheet

Claims (8)

  The 60 degree gloss in the direction parallel to the rolling direction and the direction perpendicular to the rolling direction is 500% or more, the average crystal grain size after heating for 1 hour at 1000 ° C. in an atmosphere of argon containing 20% by volume of hydrogen and the balance is 200 μm or more. A copper foil for producing graphene.   The graphene-producing copper foil according to claim 1, wherein the average crystal grain size is 400 μm or more.   The graphene-producing copper foil according to claim 1, wherein the average crystal grain size is 900 μm or more.   The copper foil for producing graphene according to claim 1, wherein the arithmetic average roughness Ra of the surface is 0.05 μm or less. Graphene-producing copper containing 20% by volume or more of hydrogen, having an average crystal grain size of 200 μm or more after heating for 1 hour at 1000 ° C. in an atmosphere of argon, and an arithmetic average roughness Ra of 0.05 μm or less Foil.   The copper foil for producing graphene according to claim 5, wherein the arithmetic average roughness Ra of the surface is 0.03 μm or less.   One or more selected from the group of Sn and Ag with respect to JIS-H3100 or JIS-H3250, oxygen-free copper specified by JIS-H3100 or JIS-H3510, or the tough-pitch copper or oxygen-free copper The copper foil for graphene manufacture in any one of Claims 1-6 containing 0.050 mass% or less of said element. A method for producing graphene using the copper foil for producing graphene according to claim 1,
A graphene forming step of arranging the heated copper foil for producing graphene in a predetermined chamber and supplying a carbon-containing gas and forming graphene on the surface of the copper foil for producing graphene,
A graphene transfer process comprising: laminating a transfer sheet on the surface of the graphene; and transferring the graphene onto the transfer sheet while etching and removing the copper foil for producing graphene.

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